10-12 September 2015

droidcon Greece Thessaloniki

App Fails and Retrospectives

App Fails and Retrospectives#Session SDK

Raymond Chenongoogle.com/+RaymondChenon

Topics

1. Zalando2. Our Google Play Release Panic3. An Internationalization Problem4. User Country Problem5. App Deep Link6. Choosing a library

One of Europe's largest online fashion retailers

15 countries3 fulfillment centers16+ million active customers2.2+ billion € revenue 20149.000+ employees

About Zalando Tech

● Tech HQ in Berlin● Four other tech offices, including Helsinki and Dublin● +800 technologists ● Nearly everything produced in-house● 135+ million visits per month (57% come from mobile

devices)

Environment

Special Thanks to “#guild-fuckup”

Valentine Gogichashvili● Head of Data Engineering● Creator of “#guild-fuckup”

on HipChat

Our Google Play Store Release Panic

Play Store Release: The Context

After one week of testing and bugfixing:100% Tests OK. QA team gave the go

The new app version was staged rollout at 50% of our users right before a long weekend.

Chronology

● 19h We noticed all app start will crash after an update.

● Issue escalated. Boss arrived .● Call to Google. Sorry Google cannot revert for

you.○ hotfix ( identify the cause first )○ create a new .apk

What Google says

Note that rollbacks aren’t supported due to the app versioning requirements of the Android platform.If you need to rollback, consider launching a previous APK with a new version number.

Understand App Versioning

Make sure that each successive release of your application uses a greater versionCode value.

NewVersion.versionCode < Rollback.versionCode

versionCode

201 202 203

Rollback Strategy

versionCode(internal)

2.3 (Old version) 2.4 (New version)

versionName( String visible to user)

101 102100

Rollback Strategy

versionCode(internal)

2.3 (Old version) 2.4 (New version) 2.3.1 (Rollback)

versionName( String visible to user)

101 102100

Rollback is built from the code base of the Old Version

Play Store Release: Lessons

- Cause of the crash : One column was renamed in the app’s SQLite database

- Always test an app upgrade- Have a rollback .apk ready - Never publish before weekends or public holidays- Limit the potential damage by starting the staged rollout

Think Google Play is Hard !!

Think Google Play is Hard !!

How this would work on iOS

- No staged rollout- No app rollback strategy- Expedited App Review ( Urgent Bug Fix ) takes

minimum 19 h ( without rejection)

When to celebrate a Release

Celebrate on the release day ….

When to celebrate a Release

Celebrate on the release day OR after user reviews

Celebrate a release one week after . It depends on the length of release cycle ( 6 week cycle )

The Internationalization Problem

Internationalization: The Context

We’re in 15 countries—but not Russia

● If the device is in Russian, Zalando’s app title was “Barcode scanner”

Internationalization

Why “Barcode Scanner?”

● We use libraries with resources: apklib, aar

● The apklib, aar library overrides our strings

app_name library’s app_name

en zalando barcode scanner

de zalando barcode scanner

ru barcode scanner

Internationalization: Lang

The locales (res/values-xx/strings.xml) are two-letter ISO 639-1 language

26^2 = 676 possibilities

You don’t have to cover all languages

Internationalization: Solutions

● app_name is the default key for the name. Rename app_name to company_app_name

● Make sure there is no key name collision

Solution Res Configs

http://tools.android.com/tech-docs/new-build-system/resource-shrinking

android { defaultConfig { resConfigs "en", "fr", "de", "gr" // languages targeted }}

A User Country Problem

Source

User Country: The Context

Device locale is NOT the same as the country where the user lives ( country of delivery )● Example: My phone is in English, but I live in Greece

Solution IP geolocation

You can resolve with IP geolocation.

Solution IP geolocation

You can resolve with IP geolocation.

But there are some edge cases , the user :- is roaming- lives in a country border

Solution IP geolocation

You can resolve with IP geolocation.

But there are some edge cases , the user :- is roaming- lives in a country border- uses a VPN

User Country: Solution 1

Mobile: you infer the user’s country by using the TelephonyManager

import android.telephony.TelephonyManager;….telephonyManager.getNetworkCountryIso();

User Country: Solution 2

Or: let the user select his/her country

Deep Link

Source

App Deep Link

App deep linking refers to a URL that points to a specific part of an app ( onboarding )

Use cases1. Link Web to App2. Link App to App3. Push Notifications , Ad Campaigns , Referral Programs ...

Example Deep Linkzalando://SEARCH?query=short https://www.zalando.de/katalog/?q=short

Error with deep links from developers

The application syncs data at initial setup phase. Loading with a Splash screen.

Splash is the entry point for all target Activities.Don’t forget to load the Splash.

Error with deep links

Take care how the deep links are used ( onboarding , home )Create a good documentation.

Deep Links are powerful API.Check how a third party would use them.

Choosing a Library

Source

Open source libraries

Commercial productsnot always your choice ( boss, budget … )

Open sourceDevelopers choose the best tool

Criteria

1. Is the API to your liking?2. Maturity level3. How well documented is the project? 4. Is the project "famous"?

Select Your Library: Lessons

What is best for X may not be for you. Do you own research.

- Always benchmark the available libraries

- Don’t let fanboy/girlism cloud your judgment

Libraries memory use

loading time ...

Picasso

Glide

Ion

Universal Image Loader

Volley

Refactoring: Some Best Practices

DO1. no behavior change (100% unit tests success)2. measurable improvement—strengthen the argument for

refactoringDON’T1. refactor without a set of tests in place

from Roboguice to Dagger 2

The library of Dependency Injection was good at that time.

Now something new came out. It made its proof.

Cannot be incremental refactoring . Must be done in one Go.

Arguments to switch from Roboguice to Dagger 2

Roboguice uses reflection ( runtime )Dagger 2 is based annotation processing ( compile time )

Performance-wise : Dagger 2 is much better than Roboguice

Big Refactoring: Lessons

● The better you prepare for changes, the fewer problems afterward

● Make sure everything compiles.

will take a photo in Greece

Raymond Chenongoogle.com/+RaymondChenontwitter.com/raychenon raychenon.com

Thank you!droidcon Greece Thessaloniki

About Zalando

Tech Blog: tech.zalando.comGitHub: github.com/zalando

Twitter: @ZalandoTechInstagram: zalandotech

Jobs: http://tech.zalando.com/jobsRefer: raymond.chenon@zalando.de